Frequency conversion speed regulation technology is an important development direction of modern electric drive technology. With the application of power electronics technology, microelectronics technology and modern control theory in AC speed regulation system, variable frequency AC speed regulation has gradually replaced the previous speed regulation systems such as slip speed regulation, pole-changing speed regulation and DC speed regulation, and has been more and more widely used in many fields of industrial production and daily life. However, due to the use environment, service life, human operation and other factors, the service life of the inverter has been greatly reduced, and various failures have also appeared in use.

Let's discuss with you some common faults and countermeasures of frequency converter:

First, you can do a static test on the inverter. General frequency converters generally include the following parts: 1 rectifier circuit, 2 DC intermediate circuit, 3 inverter circuit and 4 control circuit. Static test mainly tests the high-power transistors (power modules) in rectifier circuit, DC intermediate circuit and inverter circuit. The tools are mainly multimeters. The rectifier circuit mainly tests the positive and negative phases of the rectifier diode to judge whether it is good or not. Of course, we can also use a pressure tester to test. The DC intermediate circuit mainly measures the capacity and withstand voltage of the filter capacitor, and we can also observe whether the safety valve on the capacitor bursts and leaks. The judgment of power module is mainly the judgment of freewheeling diode in power module. For IGBT module, we also need to judge whether it can be turned on when there is a trigger voltage.

Secondly, we can judge the fault point by the display of the frequency converter.

OC。 Over-current, which may be the most common fault in frequency converter. First of all, we must eliminate the fault caused by parameter problems. For example, current limitation and short acceleration time may lead to overcurrent. Then it must be judged whether there is a problem with the current detection circuit. Take FVR075G7S-4EX as an example: We sometimes see that the panel of FVR075G7S-4EX will also have current display when there is no motor connected. Where does the current come from? It's time to test its three Hall sensors. In order to determine which phase sensor is damaged, we can turn on the machine every time we remove the phase sensor to see if there will be a current display. After this test, the OC fault can be basically eliminated.

Overvoltage, first of all, we must eliminate the fault caused by parameter problems. For example, the deceleration time is too short, overvoltage caused by regenerative load, etc. Then we can see whether there is a problem with the input voltage, and finally we can see whether the voltage detection circuit is faulty. Generally, the voltage sampling point of voltage detection circuit is the voltage of intermediate DC circuit. We take Sanken SVF303 as an example. It is sampled by a DC loop (about 530V DC), stepped down by a large resistor, and then isolated by an optocoupler. When the voltage exceeds a certain value, the "5" overvoltage is displayed (this machine uses a digital tube to display). We can see whether the resistor is oxidized or not and whether the optocoupler is short-circuited.

Undervoltage. We can see whether there is a problem with the input voltage first, and then look at the voltage detection circuit. Fault judgment is the same as overvoltage.

Fu. Quick fuse failure. At present, most frequency converters have introduced the function of fast fuse fault detection. (especially high-power inverter) Take LG030IH-4 inverter as an example. Mainly to sample and detect the voltage before and after fast melting. When the fast melting is damaged, there must be no voltage at one end of the fast melting. At this point, the isolation optocoupler acts, and a FU alarm appears. Replacing rapid melting should solve the problem. It is particularly important to note that it is necessary to judge whether there is a problem with the main circuit before replacing the fast fuse.

oh Overheating, the main reason is that the inverter internal heat dissipation is not good. We can check the cooling fan and ventilation duct.

I.e. short circuit fault. We can check whether there is a short circuit in the inverter. We take An Chuan 6 16G5A45P5 as an example. Let's check the internal circuit, it may not be short-circuited. At this time, we can check that the power module may be faulty. If the drive circuit is normal, replacing the power module should be able to repair the machine.

There are many kinds of inverter faults, which can only be summarized in practice and a set of fast and effective methods to deal with inverter faults can be found. The above is just my own experience in practice, and I will discuss it with you.